As a method for manufacturing casting molds (including various granular aggregate members of mold assembly), a urethane self-hardening mold making method or a cold box process wherein a binder containing organic solvent solutions containing primarily a polyol compound and a polyisocyanate compound, respectively, is mixed with granular aggregate such as silica sand, and the resulting mixture is charged into a pattern and hardened by urethanization reaction by the catalytic action of a tertiary amine thereby giving a desired mold is widely known and conducted. These mold making methods have advantages such as hardening ability at room temperature, rapid hardening, and excellent mold collapsibility after casting to facilitate separation from a casting, and thus these methods are increasingly used as energy-saving and highly productive mold making methods.
To prevent gas defects in the cold box process or the urethane self-hardening mold making method, a method of reducing the additive amount by increasing a binder increasing strength or a method of preventing gas defects by using various additives (JP-A 2004-255451).
In the cold box process, a method of extending bench life is disclosed (JP-A 2004-358531).
As casting sand excellent in fluidity and capable of producing a high-strength mold having a smooth surface, specific spherical casting sand is disclosed in JP-A 2004-202577.